1. Field of the Invention
The present invention relates to a device for controlling the radiating output of a semiconductor laser for use in a laser printer, for example.
2. Description of the Prior Art
The radiating output of a semiconductor laser is highly dependent on the temperature, and should therefore be stabilized by some means in environments in which the semiconductor layer is subjected to varying ambient temperatures. There has conventionally been employed a device for controlling the radiating output of a semiconductor laser used as a light source in a laser printer. The conventional device includes a photodetector for detecting the quantity of an emitted laser beam from the semiconductor laser during a period in which the laser beam is not modulated by an information signal, each time the laser beam is scanned by a beam scanning device (or in each main scanning stroke). The control device is responsive to a detected signal from the photodetector for controlling the quantity of the laser beam emission. With this prior control system, however, the photodetector used has to be of a high response speed and hence is expensive. The semiconductor laser as it operates has its power output falling when the drive current is constant. If the semiconductor laser is in a standby mode in which no recording is effected for a long period of time, the power output of the laser is reduced to a large degree, causing a problem upon recording in a next frame.